US2259634A - Means for forming castings - Google Patents

Description

Oct. 21, F. HAGEMEYER I MEANS FOR FORMING CASTINGS Filed Jan. 15, 1940 2 Sheets-Sheet 2 Patented Oct. 21, 1941 MEANS FOR FORMING CASTINGS Henry F. Hagemeyer, Chicago, Ill assignor to Castings Patent Corporation,

corporation of Illinois Application January 15, 1940, Serial No. 313,872 19 Claims. (CL 22-134) This invention relates generally to the art of forming castings and is more particularly concerned with a novel method and mold for form-- ing castings which results in the production of castings having a uniform high quality and in which porosity, lack of uniformity, the formation and entrainment of oxides and occluded gases, distortion, bad surface finish, and other well-known defects likely to be present in castings are largely eliminated.

By casting processes as ordinarily practiced,

several mold cavities are connected to a runner by feeders and the runner is in turn connected to a sprue or filling opening. The fused nietal is then poured into the sprue and runs down the runner, through the feeders and into the mold cavities, or in the case. of pressure castings is forced into the sprue. This rapid movement of the metal, together with the splashing and spraying about of the metal within the mold, causes oxides formed at. the surface of the fused metal to be mixed with the metal and to be trapped therein when the metal hardens. Also, during the process of pouring the molten metal into themold, frequently quantitles of gases and air are trapped within the castings, thereby producing a spongy structure which weakens the resulting casting and also causes the rejection of castings that are intended to be fluid tight, such, for instance, as engine or compressor cylinder blocks and heads, valves, pipe fittings, and the like.

Another disadvantage frequently encountered in ordinary casting processes is that the metal in the runner and sprue solidifies after the metal in the mold impressions. ,The subsequent shrinkage of the runner, therefore, puts considerable stress on the castings, which frequently results in the completed castings having strains therein, or in the castings being distorted.

It is the principalobject of the present invention to overcome the above generally recog nized defects in castings.

A more specific object of the present invention is to form castings by causing the fused metal to flow into and within a mold in a novel manner that minimizes the formation of oxides and gases and prevents their occlusion. and that therefore gives the resulting casting a'more homogeneous structure and a more uniform density.

A further object of the present invention is to form castings in a novel manner that prevents oxides formed at the surfaces of the fused metal from becoming entrained within the cast- 1118- I I Chicago, 111., a

An additional object of my invention is to provide an improved mold and method of molding that prevents the cooling and attendant shrinking of the castings and runnerfrom causing distortions or strains in the castings.

A still further object of the present invention is to-provide a. novel method and mold for forming castings that allows the runner to shrink away from the several castings as the runner cools without putting excessive strains on the castings.

A still further object of the present invention is to provide a novel method and mold that permits the casting of metal at lower temperatures than those customarily used, and in which a definite but relatively low pressure is used to form the impression of the mold.

Another object of my invention is to provide a mold. and casting process that keeps the oxide film on the molten metal flowing into the mold in constant motion until it touches the mold surface and thereafter prevents the movement of any metal which has been brought into contact with the mold surface.

An additional object is to provide a novel mold and casting process that permits the use of much smaller sprues and runners than customarily used.

so pending application, Serial Fig. 1;

Figs. 3, 4, 5, 6, 7 and 8 may be consideredas sectional views taken in the direction of the arrows, respectively, along the lines 3-3, 4-4, 5-5, 88, 1-1, and 8-! of Fig. 1. In these views, Figs. 3 to 8, the portionsof the mold surrounding the respective sectionsare included in the views.

In the drawings in which similar characters of reference refer to similar parts throughout the several views, the two mold halves, which will be referred to as the. drag in and cope II, are preferably formed of a gypsum base com- Pound in the manner as described in my co- No. 203,872, although it will be understood that the method oomprising the present invention is adapted for use with molds composed of other materials, such as sand, or,'in the case of pressure castings, metal.

As is the usual practice, the cope and drag each have depressions formed therein, whereby when these two mold halves are placed together, the resulting cavities will be complementary to the part to be cast, it being understood that I use separately formed core parts inserted into the mold cavities wherever this becomes necessary oradvisable. The practice of using cores and other separately formed mold parts is well understood and will not be described here, inasmuch as this invention does not contemplate any change in the use of these mold elements.

The essence of the molding method comprising my invention is to cause the metal flowing into the mold to form a globule around the point of entrance of the metal. This globule is then constantly and comparatively slowly expanded by additional metal running into the inside thereof, until the entire mold cavity is full. This I accomplish with as little turbulence in the metal as possible, and thus oxides formed at the sur- 1 face of the globule remain on the surface and are not entrained in the .molten metal. As the I globule expands, these oxides are brought against the surface of the mold cavity. whereupon the metal touching the wall becomes'chilled some-. what and its viscosity thereby increased to a point where it remains in place against the wall of -the mold and immobilizes the oxides, while the hotter and therefore more fluid metal in the interior of the globule flows through the shell of thickened metal to other portions of the imimpression at the lowest point, but if this appears to be impractical, the metal should flow into the impression as close to its lowest point as can be arranged, so that the quality of the castings will suiier as little as possible. It is also advisable to bring the metal into the im-- pression at the thickest section of the casting to be produced, so that the temperature of the metal reaching the several portions of the casti s, impression will be more constant.

As will be explained more fully later, the metal is slowed in its now into the casting impressions by a restriction placed in the path of flow of the metal rather than by having its rate of fiow determined by the venting capacity of the mold. I prefer that the'head behind the metal flowing into the mold should be sufiicient so that a pressure of about two and onehalf to three pounds per square inch will be brought to bear upon the pression. Thus, the surface film on the globule is in constant controlled motion until it touches the mold wall and thereafter cannot mix with the molten metal, nor can chunks of thickened.

metal come loose from the walls. and re-enter the still flowing metal.

In order to promote the fiow of. metal in the mold in the manner as above described, I tilt the mold, so that the metal must run uphill along the feeders and in the casting impressions which it enters at its lowest point? Between the feedersand the mold cavity, a small orifice is provided through which the metal must run. This orifice slows the rate of flow of the metal and allows the formation and gradual expansion of a globule of metal within the mold cavity. Preferably the mold is arranged that the metal flows into a casting impression at its lowest point, so that the globule' around the inlet open-= ing is formed as quickly as possible and splashing of the metal within the mold is prevented,

although practical considerations affecting the bring the metal into the casting impression slightly above the lowest point. If .the metal enters the impression'above the lowest point, it will be appreciated that a globule may not form around the inlet opening immediately, but will be formed as soon as the level ofthe molten metal in the casting impression rises to the level of the inlet opening. If the formation of this globule does not take too 10118. no serious eflects will be noticed in the casting. produced, since the metal flows, slowly into the impression andthis forms a :pool, the level of which quickly rises to cover the inlet opening without causing. the

"It may be said that,,as a rule, the mold should metal at the top of the highest impression when the mold and sprue are full. It should be ob-- served, however, that since the metal -fiows through a restriction before it reaches the impression and'fiows'into the impression at a rate slower than the venting rate of the mold, the pressure within the impression will be very low until'the impression is filled, whereupon the full head will immediately be brought to bear to form a sharp impression of the mold Since the metal is always caused to flow uphill,

I form the major portion of the impression in the cope. This is contrary to usual casting practice, but works well with the present method. It

is also usual casting practice to place the portion of the casting requiring the best finish in the drag, but with the present process the finish produced by all portions of the-impression are qually good.

In the drawings,-I have shown typical molded parts and the molds I prefer to use in carrying out my process. As shownin Fig. 3, the cope I2 is placed upon the drag l0 and the plane of juncture of these two mold halves will be referred to as the parting line I. A runner cavity l6 extends substantially down the center of the mold and joins the sprue llat one end'thereof.

This sprue extends upwardly through the cope and is further extended above the top of the mold by an asbestos paper sleeve 20, thelower end of which sets in an annular slot 22 concentric with the sprue opening in the top of the -cope. The height of the-sleeve should be such that the hydrostatic head at the top of the highest casting impression will be from about two and one-half tothree pounds when the sprue is reasonably full."

"layout of the mold may make it advisable to be laid out to bring the metal into the casting At intervals along the sides of the runner l6, branches or feeders 24 extend outwardly therefrom. These feeders 24 usually lead to a generally cylindrical cavity which .I calla shrink bob cavity "and from there the metal flows into the mold impression through a neck 21. .The purpose of this shrink bob-cavity is to provide a-re'servoir of metal that solidifies after the casting proper, and thus provides a quantity of metal which can be drawn into the casting when shrinkage in this, element takes place. By the use of this shrink bob, 1* eifectlvely prevent the formation of within the castings due to shrinkage of the metal. It will be a preciated that the casting will be removed from the mold with the. shrink bobattached thereto and that the shrink bob will-ordinarily be removed from the casting before the casting is Between the shrink bob 2' and the feeder ll,

the metal is forced to flow through a very small orifice 28 which restricts the flow of metal into the mold,'while the interposition of the shrink bob between the orifice 28 and the casting impression permits the flow of metal to be slowed flow vertically, or,

the orifice causes metal flowing .therethrough to in other words, at right angles to the outlet of the shrink bob.

In Fig. 5, which illustrates parts b, d and j in section, it will be seen that the mold is in general similar to that shown in Fig. 4. Since this part requires less metal than that shown in Fig. 4, however, the shrink bob 26, neck 21 and orifice 28 are all smaller than the similar parts in Fig. 4. In forming this mold, the feeder 2t, shrink bob 26 and neck 2! are all formed by cavities in the cope only, while the orifice is produced 'by a cavity in the drag; although it will be appreciated pression or cavity slowly and because of gravity I and its surface tension, it forms a globule which is uniformly expanded until the impression is filled. If the part to be cast is a ring or of similar shape, the globule will divide and expand around both sides of the central core until the rounded forward faces of the two expanding streams touch, whereupon the oxides covering these forward faces will be pushed aside against the surface of the mold cavity as the two streams of metal loin.

It has been found that if the partto be cast is quite small, the shrink bob may, in some instances, be dispensed with, in which event the feeder is connected directly to the casting impression by the small orifice. Such an arrangement is shown in Figs. 6 and 8.

In arranging the mold, care should be taken to see that the cross-sectional areas of the one or more runners are considerably greater than the total cross-sectional areas of the orifices leading therefrom, and that the cross-sectionai area of the sprue is several times greater than the total of the similar areas of the runners attached thereto. This is done so that when the pouring operation is started, the sprue and then the runnerswill immediately fill and bring the full hydrostatic head in the sprue to bear to force the metal through the orifices. Since the runners and sprue are kept full during the pouring operation, the danger of entraining oxides and gases is greatly lessened.

For convenience in discussing-the several castings attached to the runner in Fig. 1, those castings below the runner are lettered from a to e beginning at the sprue, while those above the runner. are similarly lettered from 7 to 1. Of these parts, those lettered a, c, and e are alike and are alternated along the runner with parts I), d and I. These parts are positioned along the.

runner much in the manner that I use for regularly producing castings, while parts 9, h, i and j are odd'parts which are illustrated for the purpose of better disclosing the present invention. The parts a, c and e, as may be seen that nothing in my process requires that these several elements be specifically so formed.

Fig. 6 illustrates a ring gear requiring a comparatively small amount of metal. For this reason the shrink bob has been omitted. Since the bottom surface of this ring gear is hat and since its total height is well within the limits of the cope alone, this part is formed by a cavity in the cope only.

The rectangular part illustrated in Fig. 7 is of considerable height and for this reason the hotsides its control over the rate of flow of -the from Fig. 4, are of compartively heavy section and it is for this reason that a comparatively large shrink bob 26 is used.

Although for practical considerations, I'have not shown the metal as running into the absolute bottom of the mold impression in Fig. 4-, it will be seen that when this mold is tilted into pouring position, as shown in Fig. 3, not much metal will need to flow into the impression before a globule is formed. This globule can then be expanded without breaking, until the mold is full. The small-orifice 28 through which the metal must run in passing from the the shrink bob is formed in this instance by overlapping slots in the cope and drag, and thus feeder to tom of the casting, together with the shrink bob 26 and neck 2?, are all formed inthe cope, but offset downwardly well below the normal parting line of. the mold. As in the case of Fig. 5, the orifice is formed by a groove in the drag overlapping the cavities in the cope. The metal is delivered from the feeder 26 to the orifice 28 by a downwardly extending feeder extension 24.

In Fig. 8 is shown a beveled pinion that is small enough to require no shrink bob. In forming this part, mold cavities are formed in both the cope and drag, while the neck leading from the orifice to the principal impression is wholly within the drag.

I The above illustrations are given merely for the purpose of showing the adaptability of the process for use in forming different types of castings and should not be'understood as limiting each of the particular parts to the particular mold arrangement shown. Each of the parts shown in Figs. 4 to 8 is illustrated somewhat smaller than full scale. It will be appreciated also that although I have shown a single runner in the drawings, I intend thatmore runners may be used if desired and that, if desired, a sprue of any suitable material of low heat conductivity may be used in place of the asbestos paper sleeve shown.

, An additional utility of the small orifice 28, be-

metal into the mold, is that after the metal inthe mold solidifies and the runner starts contracting, the metal will break .or stretch across the thin section at the orifice. That is, the interposition of this easily fractured piece between th molded pieces and the runner protectsthe molded pieces from being distorted by limiting the amount of pull to which the molded pieces can be subjected to the amount of force which is necessary to stretch or break this small section. In carrying out this function of the orifice, I prefer that the smallest portion of the orifice should be located contiguous to the body of metal which solidifies last. Withthis arrangement, the separation of the castings from the runner will ordinarily occur while the metal at the orifice isstill soft, and thus the stress on the castings is at a minimum. To reduce th pull necessary to bring about this separation even further, I prefer that the cor ners of the orifice where it'ioins the larger body of metal should be sharp and not rounded, in order to give the section'of metal at this point as of said sprue to the casting impression.

little strength as possible. It has been found, for instance, that when a'mold arrangement such as is shown in Fig. l is cast and allowed to cool and the mold material is washed or broken away. from the metal, all of the cast pieces will be found separated from the runner with the occasional exception of parts close to the sprue, such for instance as those in the positions a and f.

The size of the orifice 28 used depends in each instance upon the venting capacity of the mold the factor limiting-the rate of flow of metal into the mold is the size of the orifice rather than the venting capacity of the mold. The size of this orifice is not critical inasmuch as it may be con-. siderably smaller than the maximum mentioned above. As a general rule, I have found'that the cross-sectional area of the orifice should be approximately .000'7 square inch for each ounce of weight of the casting to be produced when the molds are constructed. in the manner described in my copending application previously referred 10. and should as a maximum be of such size that to and the alloy is of. the fluidity of yellow brass in the 60% copper-40% zincgroup. Alloys of higher viscosity will require somewhat larger orifices.

Many factors, such as the hydrostatic head used, alloy being cast, volume of the mold,'etc., influence the size of this orifice, but the figure given will serve as a starting point from which the best possible size must be determined by trial.

. bob cavity leading from said feeder, a passage leading from the shrink bob cavity to the casting impression, and means interposed between the feeder and the, shrink bob to restrict-the flow of metal into said shrink bob and casting impression to an extremely low volumetric rate.

2. A casting mold having therein a casting impression, a sprue, a runner leading from near the bottom ofsaid sprue, a feeder leading fromsaid runner, a shrink bob cavity leading from said feeder, a passage leading from the shrink bob cavity to the casting impression, means interposed between the feeder and the shrink bob to restrict the flow of metal'into said shrink bob and casting impression to an extremely low volumetric rate, said moidwhen placed in pouring position providing a substantially continuous uphill path for the flow of metal from the bottom 3. A casting mold of porous material having therein a casting impression, a sprue, a runner leading from said sprue, a feeder leading from said runner, a shrink bob cavity leading from said feeder, a passage leading from the shrink bob-cavity to a casting impression, and. means interposed between the feeder and the shrink bob'to restrict the flow of metal into said shrink bob and casting impression to an extremely low' volumetric rate, said means being such that the rate of flow of metal into said casting impression is determined by said. means rather than by theyenting rate of said mold.

4. A casting mold of porous material havin therein a casting impression, it sprue, a runner leading from said sprue, a feeder leading from said runner, a shrink bob cavity leading from said feeder, a passage leading from the shrink bob cavity to a casting impression, and means interposed between the feeder and the shrink bob to restrict the flow of metal into said shrink bob and casting impression to an extremely low volumetric rate, said means being such that the rate of flow of metal into said casting impression is determinedby said means rather than by the venting rate of ,said mold, and said mold when placed in pouring position providing a substantially continuous uphill path for the flow of metal from the bottom of said sprue to the most remote wall of said casting impression.

5. A casting mold having therein a casting impression, a sprue, a runner leading from near the bottom of said sprue, a passage leading from the runner to the lower portion of said casting impression, and means including a small orifice interposed between the runnerand the casting impression to restrict the flow of metal into said' casting impression to an extremely low volumetric rate, said means being so situated relative to the casting impression that the direction of flow through said means is substantially at right angles to the direction of flow immediately thereafter.

6. A casting mold of porous-material having therein a casting impression, a sprue, a runner leading from near the bottom of said sprue. a passage leading from the runner to the castin impression, means. interposed between the runner and the casting impression to restrict the flow ofmetal into said casting impression to an extremely low volumetric rate, and said mold when placed in pouring position providing. a continuous uphill path for the flow of metal from most remote wall of said bottom of said sprue to the casting impression.

7. A casting mold of porous material having therein a casting impression, a sprue, a runner leading from near the bottom of said sprue, a passage leading from'the runner to the casting impression, a small orifice interposed between the runner and the casting impression to restrict the rate of flow of metal into said casting impression, the cross-sectional area of saidv orifice being of the order of .0007 square inch for each ounce of weight of the casting to be produced by said impression.

-8. A casting mold having a casting impression therein, a sprue to receive fused metal, and passageways connecting the sprue to the casting impression, said passageways including a restricted portion having across-sectional area of the order of .0007 "square inch for each ounce of weight of the casting to be produced in said impression.

9. Acasting mold having a casting impression therein, a sprue to receive fused metal, a passageway connecting the sprue to the casting impression, said passageway including means having a portion of extremely small cross-sectional area-to restrict the flow of metal into said casting impression to an extremely low. volumetric rate, and said mold when in pouring position providing a continuous uphill path for the flow of metal from the bottom'of said sprue to the casting impression, whereby said casting impression will fill slowly and substantially without turbulence.

10. A casting mold having therein a casting on, a sprue, a runner leading from near the lower end of said sprue, a feeder leading from said runner, a shrink bob cavity leading from said feeder, a passage leading from the shrink bob cavity to a casting impression, and a small orifice interposed between the shrink bob and the feeder, said orifice directing the flow of metal into said shrink bob in a direction substantially normal to the direction of flow oi the metal into said casting impression and said small orifice operating to provide an easily fractured section between the impression and the runner to permit separation of the castings upon contraction of the metal.

11. A casting mold having therein a casting impression, a sprue, a runner leading from near the lower end of said sprue, a feeder leading from said runner, a shrink bob cavity leading from said feeder, a passage leading from the shrink bob cavity to a casting impression, and a small orifice interposed between the shrink bob and the feeder, said orifice directing the flow of metal into said shrink bob in a direction substantially normal to the direction of flow of the metal into said casting impression, and said mold when in pouring position providing a substantially continuous uphill path between the lower end of said sprue and the casting impression along which the fused metal must flow.

12. A casting mold having therein a casting impression, it sprue,. a passageway leading from near the lower end of said sprue to the casting impression, said passageway including an enlarged portion contiguous to said casting impression and a restricted portion contiguous to said enlarged portion, so that fused metal flowing to said casting impression from the sprue will flow through said restricted portion into the enlarged portion and from said enlarged portion to said casting impression, said restricted portion causing metal to flow into the enlarged portion in a direction normal to the direction oi flow of metal from the enlarged portion to the casting impression.

13. A casting mold having therein a casting impression. a sprue, and a passageway leading from near the lower end of the sprue to the casting impression, said passageway including a portion having a cross-sectional area of the order of .0007 square inch for each ounce of weight of the casting to be produced in said impression.

14. A casting mold having therein a casting impression, a sprue, and an uphill passageway leading from near the lower end of said sprue to the casting impression, means for restricting the flow of metal in said passageway including a restricted portion of comparatively minute crosssectional area adjacent the casting impression, whereby the flow of metal into said casting impression will be at an extremely low volumetric rate and said casting impression will fill slowly and substantially without turbulence.

15; A casting mold having therein a casting impression, a sprue, and a passageway leading from near the lower end of said sprue to the casting impression, means in said passageway in eluding a restricted portion of comparatively minute cross-sectional area adjacent the casting impression for reducing the flow oi said metal to an extremely low volumetric rate and said means being so disposed that the direction of flow of metal therethrough is substantially at right angles to the direction of flow oi the metal immediately thereafter.

16. A casting mold having therein a casting impression, a sprue, a passageway leading substantially continuously uphill from near the lower end of the sprue to the casting impression, and means in said passageway to restrict the flow of metal into the casting impression, to an extremely low volumetric rate, whereby said casting impression will illl slowly and substantially without turbulence.

17. A casting mold having therein a casting impression, a sprue, and a passageway leading from near the lower end of said sprue to the casting impression, said passageway including means to restrict the volumetric flow therethrough, means forming a turbulence damping expansion chamber, means directing the flow of metal from said restricting means to said expansion chamber, passage means for conducting the metal from the expansion chamber to the mold impression, and the last said passage means being connected to said expansion chamber at an angle to the connection between the expansion chamber and said flow directing means.

18. A casting mold having therein a casting impression, a sprue, a passageway inclined generally upwardly from near the lower end of said sprue to the casting impression, said passageway including means to restrict the volumetric rate of flow of metal to said casting impression, and means positioned between said restricting means and said casting impression to reduce the jet action of the metal flowing through said restricting means before said metal reaches said casting impression, whereby the flow of metal to said casting impression will be at a low volumetric rate and whereby additionally, said metal will become quiet before flowing into said casting impression so that said casting impression will fill slowly an substantially without turbulence.

19. A casting mold having therein a casting impression, a sprue, a passageway leading upwardly from near the lower portion of said sprue to said casting impression, said impression being at substantially the same angle as said passageway, and means in said passageway to restrict the flow of metal to said casting impression to cause the flow of metal to said casting impression to be at a low volumetric rate and whereby said metal will flow uphill in said casting impression slowly and substantially without turbulence.

HENRY F. HAGEMIEYER.

w CERTIFICATE OF CORRECTION. Patent No. 2,259,69 a October 21, 191,1.

HENRY F. HAGEZIEYER.

It is hereby certified that error appears in the printed specification of the, above numbered patent requiring correction as follows: Page 1;, sec- 0nd column, .lines 59 and 11.0, claim 6, strike out the words "most remotewall of said bottom of said sprue to the" and insert instead -the bottom of said sprue to most remote 'wall of said--; and that the said Letters Patent should be read with this correction therein that the same may conform to the record ofthe case-1n the Patent Office. v

Signed and sealed this 2nd day of December, A. 19141.

Henry Van Arsdale, v (Seal) Acting Commis sionen of Patents.

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